Project 1 Abstract The focus of this project is Age-related hearing loss (AHRL, presbyacusis), a widespread condition due to age related changes along the auditory pathway. Great strides have been made elucidating the peripheral changes, but age related changes in the central nervous system remain largely unknown. The project revolves around the hypothesis that cortical plasticity can play an effective role in maintaining effective auditory function in old age, by countering diminished synaptic depression and rewired inhibitory circuits. The project describes a series of behavioral and neurophysiological/imaging experiments in aged animals, which explore the physiological and behavioral correlates of ARHL and propose experiments to test how cortical plasticity could be directed to counter it. In pursuit of these goals, behavioral, neurophysiological, and imaging approaches are combined to characterize the encoding of speech in noise in aged animals and characterize how cortical plasticity which enhances the robustness of speech perception in noise in the young is inefficient in the aged. The project then goes on to study the cellular mechanisms that fail with age, and develop therapeutic strategies through plasticity induced by engagement of cognitive functions. The project exploits many technologies to achieve its goals such as single-unit recordings, in vivo 2-photon imaging in passive and the behaving animals and in vitro circuit mapping approaches. The final aim of the project is to develop remedial interventions and adaptive training procedures to reverse some of the age-related changes. 1